Add test and fix ci

tests/core/relay/test_circuit_v2_transport.py

@@ -11,6 +11,7 @@ from libp2p.network.stream.exceptions import (
     StreamEOF,
     StreamReset,
 )
+from libp2p.peer.peerinfo import PeerInfo
 from libp2p.relay.circuit_v2.config import (
     RelayConfig,
 )
@@ -344,3 +345,78 @@ async def test_circuit_v2_transport_relay_limits():
 
         # Test successful - transports were initialized with the correct limits
         logger.info("Transport limit test successful")
+
+
+@pytest.mark.trio
+async def test_circuit_v2_transport_relay_selection():
+    """Test relay round robin load balancing and reservation priority"""
+    async with HostFactory.create_batch_and_listen(5) as hosts:
+        client1_host, relay_host1, relay_host2, relay_host3, target_host = hosts
+
+        # Setup relay with strict limits
+        limits = RelayLimits(
+            duration=DEFAULT_RELAY_LIMITS.duration,
+            data=DEFAULT_RELAY_LIMITS.data,
+            max_circuit_conns=DEFAULT_RELAY_LIMITS.max_circuit_conns,
+            max_reservations=DEFAULT_RELAY_LIMITS.max_reservations,
+        )
+
+        # Register test handler on target
+        test_protocol = "/test/echo/1.0.0"
+        target_host.set_stream_handler(TProtocol(test_protocol), echo_stream_handler)
+        target_host_info = PeerInfo(target_host.get_id(), target_host.get_addrs())
+        client_config = RelayConfig()
+
+        # Client setup
+        client1_protocol = CircuitV2Protocol(client1_host, limits, allow_hop=False)
+        client1_discovery = RelayDiscovery(
+            host=client1_host,
+            auto_reserve=False,
+            discovery_interval=client_config.discovery_interval,
+            max_relays=client_config.max_relays,
+        )
+        client1_transport = CircuitV2Transport(
+            client1_host, client1_protocol, client_config
+        )
+        client1_transport.discovery = client1_discovery
+        # Add relay to discovery
+        relay_id1 = relay_host1.get_id()
+        relay_id2 = relay_host2.get_id()
+        relay_id3 = relay_host3.get_id()
+
+        # Connect all peers
+        try:
+            with trio.fail_after(CONNECT_TIMEOUT):
+                # Connect clients to relay
+                await connect(client1_host, relay_host1)
+                await connect(client1_host, relay_host2)
+                await connect(client1_host, relay_host3)
+
+                await client1_discovery._add_relay(relay_id1)
+                await client1_discovery._add_relay(relay_id2)
+                await client1_discovery._add_relay(relay_id3)
+
+                logger.info("All connections established")
+        except Exception as e:
+            logger.error("Failed to connect peers: %s", str(e))
+            raise
+
+        selected_relay = await client1_transport._select_relay(target_host_info)
+        # Without reservation preferance
+        # Round robin, so 1st time must be relay1
+        assert selected_relay is not None and selected_relay is relay_id1
+
+        selected_relay = await client1_transport._select_relay(target_host_info)
+        # Round robin, so 2nd time must be relay2
+        assert selected_relay is not None and selected_relay is relay_id2
+
+        # Mock reservation with relay1 to prioritize over relay2
+        relay_info3 = client1_discovery.get_relay_info(relay_id3)
+        if relay_info3:
+            relay_info3.has_reservation = True
+
+        selected_relay = await client1_transport._select_relay(target_host_info)
+        # With reservation preferance, relay2 must be chosen for target_peer.
+        assert selected_relay is not None and selected_relay is relay_host3.get_id()
+
+        logger.info("Relay selection successful")